1. Field of the Invention
The present invention relates to a pointing device utilized as an operating device for an electronic apparatus such as a mobile phone, a PDA, or a game controller, and to a key sheet for the pointing device. In particular, the present invention relates to a magnetic detection type pointing device which detects a change in magnetic flux density resulting from movements of a magnet, and to a key sheet for the pointing device.
2. Description of the Related Art
Nowadays, operating devices of electronic apparatuses and input systems thereof have been diversified. In this context, a magnetic detection type pointing device is known, in which a change in magnetic flux density due to “sidewise movement” of a magnet, such as tilting or horizontal displacement of the magnet, is detected by a magnetic sensor, and in which the change thus detected is utilized as an input signal. This technique is disclosed, for example, in JP 2000-235822 A, JP 2004-62447 A, and JP 2002-150904 A. In those pointing devices, a magnet is integrally accommodated in a key top to be depressed, and is moved through operation of the key top, with the movement amount of the magnet being detected by a magnetic sensor provided on a board.
In such magnetic detection type pointing devices, in which the magnet moves, there is provided some contrivance in terms of arrangement to prevent the magnet and the magnetic sensor from coming into contact with each other. For example, in the pointing devices as disclosed in JP 2000-235822 A and JP 2004-62447 A, the magnetic sensor is mounted on a back surface of the board, and even if the key top moves on the board, it does not come into contact with the magnetic sensor. However, when the magnetic sensor is provided on the back surface of the board, a distance between the magnetic sensor and the magnet is larger than in the case in which the magnetic sensor is provided on a front surface of the board, so it is necessary to use a powerful magnet. Further, it is necessary to provide a mounting space for the magnetic sensor on the back surface of the board, with the result that a thickness of the pointing device becomes rather large.
In contrast, in the technique as disclosed in JP 2002-150904 A, the magnetic sensor is mounted on the front surface of the board, so the distance between the magnetic sensor and the magnet is shorter as compared with the case in which the magnetic sensor is mounted on the back surface of the board. However, the magnet is provided inside the key top for input operation, so it is all the same necessary to use a powerful magnet, and the thickness of the magnet cannot help but be rather large. As a result, peripheral members are adversely affected by a strong magnetic field generated, and the thickness of the key top cannot be reduced due to the thickness of the magnet.